On Sun, Dec 16, 2018 at 10:41 PM Eric Dumazet <eduma...@google.com> wrote: > > On Sun, Dec 16, 2018 at 10:35 PM Peter Oskolkov <posk.de...@gmail.com> wrote: > > > > I guess DCCP is not used to the extent that 10 listeners per bucket > > happen in real life scenarios, so the issue is purely theoretical; as > > my patch would cause a sefgault for even a single listening dccp > > socket, I felt it was my patch that the "Fixes" tag should refer to. > > > > Problem is : any host with a buggy kernel can trivially crash if a > malicious application > knows about this bug and exploit it. > > This means we need to backport this fix to all kernels up to the real > root cause, > not only net-next on which your patch revealed this old bug. > > Therefore we need a correct Fixes: tag so that proper stable > submissions can be done. > > The Fixes: tag accuracy is paramount.
Make sense. I'll re-send the patch withe the correct Fixes tag asap. > > Thanks. > > > On Sun, Dec 16, 2018 at 9:51 PM Eric Dumazet <eric.duma...@gmail.com> wrote: > > > > > > > > > > > > On 12/16/2018 03:42 PM, Peter Oskolkov wrote: > > > > Commit d9fbc7f6431f "net: tcp: prefer listeners bound to an address" > > > > removes port-only listener lookups. This caused segfaults in DCCP > > > > lookups because DCCP did not initialize the (addr,port) hashtable. > > > > > > > > This patch adds said initialization. > > > > > > > > The only non-trivial issue here is the size of the new hashtable. > > > > It seemed reasonable to make it match the size of the port-only > > > > hashtable (= INET_LHTABLE_SIZE) that was used previously. Other > > > > parameters to inet_hashinfo2_init() match those used in TCP. > > > > > > > > V2 changes: marked inet_hashinfo2_init as an exported symbol > > > > so that DCCP compiles when configured as a module. > > > > > > > > Tested: syzcaller issues fixed; the second patch in the patchset > > > > tests that DCCP lookups work correctly. > > > > > > > > Fixes: d9fbc7f6431f "net: tcp: prefer listeners bound to an address" > > > > > > > > > Strange, I would say bug was brought by commit 61b7c691c731 > > > ("inet: Add a 2nd listener hashtable (port+addr)") > > > > > > The secondary hash table would have been used anyway if some application > > > (syzkaller-like) > > > had been using DCCP a bit more, to the point the second hash table would > > > have been used. > > > > > > With more than 10 listeners on one bucket, code in > > > inet6_lookup_listener() would > > > have attempted to deref a NULL pointer.